This invention relates to an improved illuminating arrangement for instrument panels and pushbuttons, such as found on calculators, telephones, and numerous other pushbutton and non-pushbutton displays. More particularly, the present invention relates to an improved illuminating arrangement of the type using the technique of edge illumination of transparent plastics. The present invention also relates to improved pushbutton retention arrangements for use in illuminated arrays.
It has been long known to utilize solids which diffuse light rays in illuminating arrangements by bringing only a fragment of the surface of such a solid into proximity with a light source so as to illuminate the entire solid as well as to facilitate the transfer of light from the solid to closely positioned indicia or other components which are desired to be illuminated. However, in those instances wherein the light is desired to be transmitted from the light diffusing solid to one or more other components, such as the pushbuttons of an instrument, the prior art arrangements have required that either one surface be coated or joined to a material, such as mirror silver, so as to deflect the light rays towards the other areas to be illuminated, or the other areas or elements had to be brought into the direct path of the light through the light diffusing solid.
U.S. Pat. Nos. 2,831,453; 3,135,470; and 3,892,959 are representative of the first-mentioned type of edge-lit display wherein reflective coatings or backings are applied to the rear of a transport sheet for the purpose of deflecting light outwardly through the frontal surface, while U.S. Pat Nos. 2,476,257; 3,144,643; 3,213,269 and 3,645,227 are representative of the latter-mentioned arrangement wherein illumination is achieved by placing the element to be illuminated in the direct path of light from the light source.
Accordingly, it is an object of this invention to provide an illuminating arrangement which utilizes a light diffusing sheet-type light-pipe, but does not require the use of reflective material or the imposition of components within the direct light path for illuminating various components and graphics.
It is a further object of this invention to provide an improved arrangement which optimizes the illumination achieved in pushbutton type devices, such as calculators and the like.
It is still a further object of this invention to achieve the above-noted improvements in a manner that provides a high degree of flexibility in adapting a single arrangement to a number of different formats.
In accordance with the present invention, a convenient low cost illuminating arrangement is achieved in the context of pushbutton devices, such as calculators, through the use of an edge-lit light-pipe sheet which has portions of its rear surface selectively roughened, such as by etching, so as to deflect light through its front surface to graphics and pushbuttons which are sought to be illuminated. Improved illumination of the pushbuttons is acheived in a preferred embodiment by providing the pushbuttons with laterally extending flanges, while improved graphics illumination is facilitated by providing apertures through these flanges such that light from the light-pipe can directly impinge upon the graphics while illuminating the pushbuttons via diffusion. To prevent obstruction of the light passing to the graphics and/or increase the illuminated area about the pushbuttons, the pushbuttons are held within their operation openings by retaining means engaging only corners of the flanges.
The above and other objects and features of the present invention will be apparent to those of ordinary skill in the art from the following detailed description when considered in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.